Spotlights (e.g., MR16 lamps) are extensively used in many lighting applications today. Usually, spotlights can include two parts: an electronic transformer; and a high power consumption quartz lamp. With increasing light-emitting diode (LED) applications in the lighting field, it has become an irreversible trend of replacing traditional quartz lights with LED lights. However, because the output of an electronic transformer in a traditional lighting circuit (e.g., for quartz lights) is typically a high-frequency low-voltage AC power supply, while LED lamps require a constant DC current source, a mismatch problem can occur between an input power supply and a load. Therefore, an effective LED driver may be needed for converting the high-frequency low-voltage AC power supply to a constant DC current source for LED applications.